Difference Between Allopatric And Sympatric Speciation

What is Speciation?

Speciation is defined as the natural productive process through which new species are created from already existing species. This process is achieved by mechanisms including genetic drift, mutation, and natural selection. Speciation in evolution creates biodiversity. It needs reproductive isolation for success. New species evolve with genetic change. Genetic mutation helps in species formation too.

The reproductive isolation blocks the gene flow. Mating barriers that may be prezygotic or postzygotic do not allow cross-breeding between two evolving populations. These mechanisms work together naturally. They cause the formation of new species. This helps species formation on Earth. Genetic drift and natural selection drive change.

Allopatric Speciation

Allopatric speciation takes place in the geographical isolation of a species into distinct subspecies. This results in the formation of new species. It has the effect of keeping the isolated groups physically separated and thus does not allow gene flow from one group to the next. This enables the groups to evolve in different manners.

Mechanism of Allopatric Speciation

Geographic Isolation: Rivers, mountains, or seas separate the members of a population from each other, causing distinct divisions. Each group faces new environments.

Divergent Evolution: The groups of population get separated and are exposed to various environmental conditions and gene changes, which, in due course, give rise to genetically diverse populations adapting to their surroundings. New species evolve with adaptation and habitat.

Examples of Allopatric Speciation

Darwin's Finches: All those finch species that are seen at present evolved from the same ancestor. This showed allopatric speciation. However, the situation on every island is different. New species evolve due to isolation. This shows clear reproductive isolation effects.

Grand Canyon Squirrels: Kaibab squirrel lives on the north rim. Abert’s squirrel lives on the south rim. They are separated by the Grand Canyon. No gene flow occurs between them. Allopatric speciation caused their divergence.

Sympatric Speciation

Sympatric type of speciation in which the evolution of a new species from an original ancestor species occurs physically in the same region. It is the type of speciation that happens when no geographical isolation of the population is involved. Reproductive isolation happens within the same region. This leads to genetic variation buildup. Populations change through mutation and selection.

Mechanism of Sympatric Speciation

Reproductive Isolation within the Same Geographic Area: Species in a population adapt to new conditions and develop characteristics that make them unsuitable for mating with other populations, even when they are in the same geographical region.

Role of Polyploidy and Selection: Polyploidy causes chromosome number changes. This triggers instant reproductive isolation events. Sexual selection affects mate choice. Habitat differentiation drives ecological adaptations. Different environments cause quick speciation events. All lead to sympatric speciation formation. New species evolve within the same region.

Examples of Sympatric Speciation

Apple Maggot Flies: These flies have diverged into various subgroups depending on the type of fruit they are attracted to, while some go for apples, others go for hawthorn. This causes reproductive isolation over time. Habitat differentiation drives their divergence. New species evolve without migration.

Cichlid Fish in African Lakes: All live in the same water body. Different species choose different mating niches. Sexual selection causes a mate preference shift. Reproductive isolation keeps them genetically separate. Sympatric speciation occurs in the same lake. New species evolve from shared ancestors.

Comparison Between Allopatric and Sympatric Speciation

Speciation explains how new species evolve. It occurs through different natural processes. Allopatric and sympatric speciation are key types. Both involve genetic variation and evolution. The main difference lies in geographic isolation. Both show how reproductive isolation develops. Each leads to the formation of new species.

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MCQs on Difference Between Allopatric And Sympatric Speciation

Question: Assertion (A): Sympatric speciation results from geographic isolation.

Reason (R): Allopatric speciation results from reproductive isolation.

1. A and R, are correct and R explains A

2. A and R, are correct but R not explains A

3. A is wrong and R is correct

4. Both A and R are wrong

Answer: A portion of the population becomes geographically separated from the main population during allopatric speciation. The population eventually splits apart completely to become a new species. A small portion of the original population becomes reproductively isolated during sympatric speciation. An entirely new subspecies appears as the isolating mechanism. A new species eventually emerges over time.

Hence, the correct answer is Option (4) Both A and R are wrong.

Question: Which speciation entails the appearance of a new species within the geographic range?

1. Sympatric speciation

2. Allopatric speciation

3. Parapatric speciation

4. Peripatric speciation

Answer: Option (1)-Speciation happens when two populations of identical species live together without interbreeding is known as sympatric speciation. The development of new species occurs within the geographic range of the parental population.

Option (2)- Allopatric speciation occurs when geographical changes cause biological populations of the same species to become isolated from one another.

Option (3)- Two or more new species can arise from one common ancestor through a process known as parapatric speciation.

Hence, the correct answer is option 1) Sympatric speciation

Question: Assertion (A): The process of creating new species is known as speciation.

Reason (R): The deme shares a common genetic base.

1. A and R, are correct and R explains A

2. A and R, are correct but R does not explain A

3. A is wrong and R is correct

4. A is correct and R is wrong

Answer: Speciation is the process through which a new species emerges from an already existing one. A species is made up of different demes. A deme is a collection of populations that share a gene pool.

Hence, the correct answer is Option (2) A and R are correct, but R does not explain A.

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• Lamarckism and theory

• Miller-Urey Experiment